"Vaporization and Liquefaction" PPT courseware on physical states and their changes

"Vaporization and Liquefaction" PPT courseware on physical states and their changes

【Experience 1】Vaporization phenomenon in life

Activity 1: Wet clothes dry faster on a sunny day than on a cloudy day. Wet clothes dry faster when there is wind than when there is no wind. Spreading wet clothes out to dry makes them dry faster than putting them together.

Activity 2: When you first come out of the swimming pool, you will feel ________.

Activity 3: When the water in the pot is "boiling", a large amount of ________ is produced. Stop heating and boil ________.

Tips: Quick, Quick, Quick, Cold Bubbles Stop

【Experience 2】Liquefaction phenomenon in life

Activity 1: ________ will appear on the outer wall of the beverage bottle just taken out of the refrigerator.

Activity 2: In the severe winter, if you wear glasses and enter a warm room, the lenses will become ________.

Tip: Water droplets are blurry

pre-study questions

1. What are vaporization and liquefaction? What are the characteristics of vaporization and liquefaction?

2. What are the factors that affect the speed of evaporation?

3. What are the characteristics of water when it boils?

4.What is the method of liquefaction?

Exploration 1 Evaporation

Combined with "Experience 1", think about the following questions

1. From "Activity 1", what are the factors that affect the speed of evaporation?

Tip: Wet clothes dry faster on a sunny day than on a cloudy day, which means that the higher the temperature, the faster the evaporation; wet clothes dry faster when there is wind than when there is no wind, which means that the air above the liquid surface flows faster and the evaporation is faster; Wet clothes dry faster when spread out to dry than when they are lumped together, indicating that the larger the surface area of ​​the liquid, the faster it evaporates.

Reference answer: temperature, air flow, surface area of ​​liquid

2. According to "Activity 2", you feel cold when you just come out of the swimming pool. What does it mean?

Tip: Because there is water on the surface of the body after coming out of the swimming pool, the evaporation of the water takes away the heat on the surface of the body. So I felt cold.

Reference answer: Evaporation (vaporization) absorbs heat

Explore 2 Characteristics of temperature changes when water boils

Combined with Activity 3 of "Experience 1", think about the following questions

1. Conjectures and assumptions:

Combined with Activity 3 of "Experience 1", if the water remains boiling after boiling, it needs to continue to __________. The temperature of the water ________.

Tip: In "Experience 1 Activity 3", when the water boils, stop heating, and the water will stop boiling. This means that when the water boils, you need to continue heating to maintain the boiling state. Use a thermometer to measure the temperature of water when it boils. It can be seen that if the water continues to be heated after boiling, the temperature will not change.

Reference answer: Heating remains unchanged

2. Experimental design:

(1) Measuring instrument: Use ________ to measure the temperature of a liquid.

Reference answer: Thermometer

(2) Assemble the equipment and record the temperature every 1 minute when the water temperature is close to 60°C.

Exploration 3 Liquefaction

Combined with "Experience 2", think about the following questions

1. Combined with "Activity 1", why do water droplets appear on the outer wall of the beverage bottle just taken out of the refrigerator? What does this mean?

Reference answer: When water vapor from the outside encounters a cold beverage bottle, the gaseous water vapor turns into small liquid water droplets. This is a liquefaction phenomenon, and liquefaction releases heat.

2. What are the two ways to liquefy gas? What are the benefits of liquefying gas?

Tip: According to the heat released by liquefaction, the temperature can be lowered to a low enough level. In addition, the compressed volume can also liquefy the gas. After the gas is liquefied, its volume shrinks, making it easier to store and transport.

Reference answers: (1) Reduce temperature (2) Compress volume

After the gas is liquefied, its volume shrinks, making it easier to store and transport.

3. What is the relationship between liquefaction and vaporization?

Reference answer: Liquefaction and vaporization are reverse processes of each other. Vaporization absorbs heat and liquefaction releases heat.

Knowledge summary

1. Vaporization

(1)Definition: The process by which matter changes from _____ to _____.

(2) Features: Vaporization _____.

(3) There are two ways of vaporization: evaporation and boiling.

2.Liquefaction

(1)Definition: The process by which matter changes from _____ to _____.

(2) Features: Liquefaction _____.

(3) Two methods of liquefaction: _________ and _________.

(4) Advantages of liquefaction: The gas volume is increased to facilitate storage and transportation.

Test point 1: Determine the phenomena of vaporization and liquefaction

[Typical example 1] (2012 Qiandongnan High School Entrance Examination) Li Qiang, a student wearing glasses, entered the warm classroom from outside in winter and found that the lenses of his glasses "breathed". After a while, the "breathed" gradually disappeared from the middle, and "breathed" "It is formed by water vapor in the air______. The disappearance of "gas" is due to the occurrence of ________ phenomenon.

[Guidance of ideas] The key to answering this question is to analyze the key words and implicit conditions of the question. The analysis ideas are as follows

[Exquisite analysis] The temperature in the classroom is very high in winter, which causes the temperature of the water vapor in the surrounding air to rise. When it encounters the lower temperature glass lens, the hot water vapor liquefies and turns into small water droplets. On the lens, so "gas" appears on the lens; after a period of time, the small water droplets on the lens will absorb heat and turn into water vapor and dissipate in the air, and the "gas" on the lens disappears, which is vaporization. Phenomenon.

Answer: Liquefaction Vaporization

[Method Summary] Determine vaporization and liquefaction

(1) Judgment method: Judgment based on the initial and final states of the object.

(2) The difference between "white gas" and water vapor.

① "White gas" is small water droplets formed when water vapor is cooled and liquefied, not water vapor.

② "White gas" is liquid and water vapor is gaseous.

Test point 2: Explore the boiling of water

[Typical Example 2] Picture A is a diagram of the experimental device for "observing the boiling of water".

(1) Xiao Cong observed that the bubbles in the water rise differently before and after the water boils, as shown in Figures B and C. The picture ______ is the condition of water before it boils. In order to easily read the thermometer's indication, Xiao Cong took the thermometer out of the water and observed the reading. This will cause the measured temperature to deviate from ______ (optional "high" or "low").

(2) When water boils, the thermometer displays as shown in Figure D. The reading is _____℃, indicating that the air pressure at this time is _____ standard atmospheric pressure (optional "greater than", "equal to" or "less than").

(3) Figure 5, Figure 6, and Figure Geng are images of the temperature of water changing with time made by three students. The correct one is Figure _____. Analyzing this image, it can be seen that the temperature remains unchanged when water boils, but it continues to _____Heat (optional "suck" or "release").

[Guidance of Thoughts] There are three key points to answer this question:

Key point 1: The bubbles change from large to small before boiling, and the bubbles change from small to large during boiling.

Key point 2: The boiling point of liquid increases with the increase of pressure.

Key point 3: The liquid absorbs heat when it boils, the temperature does not change, and the image has a horizontal part.

1. The picture is a photo of morning fog taken by a classmate in the Shangri-La Scenic Area in Yunnan. The formation process of fog belongs to ()

A.LiquefactionB.Vaporization

C. Solidification D. Melting

[Analysis] Choose A. This question tests the judgment of the types of changes in the state of matter. Liquefaction is the change from gaseous state to liquid state; vaporization is the change from liquid state to gaseous state; solidification is the change from liquid state to solid state; melting is the change from solid state to liquid state. Fog is the formation of small droplets. Hot water vapor turns into small droplets when encountering the surrounding cold environment. It is a liquefaction phenomenon, so choose A.

2. Among the phenomena described below, which one belongs to vaporization ()

A. Melt iron into molten iron B. Dry wet clothes

C. River water turns into ice D. “White gas” appears above boiling water

[Analysis] Choose B. This question tests knowledge of changes in the states of matter. The melting of iron blocks into molten iron is a melting phenomenon, the drying of wet clothes is a vaporization phenomenon, the freezing of river water is a solidification phenomenon, and the "white gas" that appears above the boiling water is formed by the liquefaction of the water vapor emerging from the boiling water. Item B correct.

3. The blackboard that has been wiped with a wet rag dries after a while. This phenomenon is ()

A. Vaporization B. Solidification

C. Liquefy D. Melt

[Analysis] Choose A. This question tests the judgment of changes in the state of matter. After wiping the blackboard with a wet rag, the moisture on the blackboard absorbs heat from the air and turns into water vapor and evaporates, changing from liquid to gas, which is a vaporization phenomenon. Therefore choose A.

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